copy video streamencode german audio stream to mp3 (128kbps) and aac (96kbps) (creating 2 audio streams in the output)drop english audio streamcopy subtitle streamThis can be done using the following FFmpeg command line:

read the input file 'input.mkv'select all the input streams (first input = 0) to be processed (using "-map 0")mark all the streams to be just copied to the output (using "-c copy")mark just the video streams to be re-encoded (using "-c:v mpeg2video")write the output file 'output.mkv'